Saito FA 115 - tappets bone dry

Hey guys i have a saito FA 115 that bit me on the hand. I left it sitting for a month and a half afterwards without adding any after run oil or whatever into the breather nipple, although i had added oil into the engine through the glow plug hole.
Anyway i finally maidened it today but was disappointed to find that after 3 or 4 minutes flying there's a rattling sound coming from the engine. i landed and a group of us stood around trying to figure it out. We removed the rocker covers and found that the tappets were bone dry. Poured some fuel into them and replaced the rocker covers and flew nicely again for a few minutes, but then the same thing happened again.
It seems theres no oil getting into the rockers and theyre rattling as a result. I have this engine mounted upright in a hangar 9 pulse xt 60 (overkill i know :-) ).

I've been advised to pump fuel into the breather nipple and stand the plane vertical on its nose for a few days, as its suspected that there is gunk build up on a bearing or something and its blocking the passage for the oil to get up top. It was suggested that the fuel will break the gunk up.

Has anyone else had this problem and if so, whats the solution?

Would really appreciate any tips on this. I just wanna fly this thing. :-)